1. Field of the Invention
The invention relates to a fire stop for sealing the space between a conduit, in particular a flue, and the periphery of an opening in a structural member through which the conduit passes.
2. Description of the prior art
When installing pre-fabricated chimney flues or ducts of stainless steel, galvanised steel or pre-cast concrete it is essential to seal the opening through which the chimney flue passes in order to restrict the passage of flame, smoke and gases in the event of a fire.
One of the methods used where the chimney flue is to be installed in a building constructed of concrete or a building with concrete slab floors is to first install the chimney flue in the desired position and cast the floor around the flue.
One disadvantage of this method is that considerable accuracy of installation is required as there is no scope for changing the position of the flue after the floor has been cast around it. In additiion, there is a risk that the chimney flue will be damaged during subsequent work operations. Further, the main construction activity is disrupted while the chimney flue is installed. Another disadvantage is that it is difficult to remove sections of the installed chimney or flue unit for repair or replacement. A further disadvantage which is especially apparent with conduits or flues of steel material is that because the duct or flue is fixed into position on heating the expansion of the flue results in buckling and subsequent rupture of the flue with a consequent escape of flame and gases.